This study focuses on measures of physiologic vascular properties and EBCT-defined extent of coronary atherosclerotic burden (as well as MRI-defined extent of carotid atherosclerotic burden) in different volunteer and patient populations. It is hypothesized that individuals with functional vascular measures similar to individuals much younger than themselves will have less atherosclerosis than those with "normal" values for their age, and that individuals with structural and functional vascular measurements similar to individuals older than themselves will have more atherosclerosis. Thus, by relating the dissociation between physioiogic 'and chronologic aging to atherosclerosis, investigators seek to define (and compare) "successful" versus "usual" versus "accelerated" cardiovascular aging. If a relationship can be demonstrated between any physiologic vascular change and coronary atherosclerotic disease, it would establish a rationale for targeted interventions designed to arrest or reverse the vascular processes that contribute to atherosclerosis, the leading cause of morbidity, mortality, and loss of independence in the older population.